Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Long-Term Borrowings and Other Financing Instruments (Details) (First Mortgage Bonds, Series Due June 15, 2024, USD $)	1 Months Ended
	Jun. 30, 2014
First Mortgage Bonds | Series Due June 15, 2024
Debt Instrument [Line Items]
Face Amount	$ 100,000,000
Interest Rate, Stated Percentage	3.30%
Maturity Date	Jun. 15, 2024